Wire-connector



Aug- 30, 1960 E, w. BOLLMEIER ET AL 2,951,109

WIRE-CONNECTOR Filed May 18, 1956 Vokaty, New Canada Township, RamseyCounty, Minn.,lassignors to Minnesota Mining and Manufacturing Company,St. Paul, Minn., a corporation of Dela- Ware Filed May 1S, 1956, Ser.No. 585,757

5 Claims. (Cl. 174-84) This invention relates to the connecting ofinsulated conductors by a simplified procedure and employing novelconnector devices permitting the formation of permanent electricalconnections in a rapid simplified manner and without any necessity offirst removing the insulating cover of the conductor.

The invention is particularly significant in the installation oftelephone equipment employing small copper Wires insulated withcoverings of treated paper or plastic film materials. The connection ismade rapidly, without tools or applicators other than conventionalpliers or side-cutters, and without requiring either the preliminaryremoval of insulation or the subsequent soldering of the connection.Effective electrical contact is provided; and such contact ispermanently maintained even under repeated mechanical stress andvibration.

The invention provides novel connector devices which may be made in awide variety of specific shapes and for a great number of speciticapplications, but which in all cases employ novel principles and providenovel structure as will now be more fully pointed out in terms ofspecific but non-limitative examples.

In the drawings:

Figure 1 is a plan View, and Figure 2 a corresponding elevation of aspring connector made in accordance with the principles of the inventionand designed for interconnecting a plurality of insulated conductors;

Figures 3-6 are plan views of spring connectors'employing the sameprinciples but designed primarily for connecting single conductors tovarious types of electrical outlets; and

Figures 7 and 8 are cross-section and end views respectively of acompound-helix multiple-conductor connector.

The connector of Figures 1 and 2 consists essentially of a series ofclose-wound cylindrical spring wire helices 10a, 10b, 10c and 10d. Eachhelix is connected to the adjacent helix or helices by an extension ofthe spring wire of which the device is formed. The longitudinal axes ofthe several helices are in the same plane and parallel to, but somewhatremoved from each other. The wire tip 111 at the end of the device willbe seen to extend from an end coil of the helix lila in a tangentialplane and at an angle with the plane of the terminal coil, i.e. at anincreased pitch angle. Generally the same configuration is found withrespect to the wire extension and the terminal coil at each end of eachof the helices. There is provided a wedge-shaped throat or openingbetween the wire extension and the corresponding segment of the endcoil. This opening provides for the insertion of a segment of aninsulated wire conductor 12 between the extended tip and the end coil.The conductor may then be slid along the convolutions of the helix andinto the position illustrated at helix tlc of Figure 1. During thissliding action, the high unit pressure provided by the strongclose-wound coils of the helix, and the frictional force exerted on theinsulated tice conductor by the sliding action, disrupt and displace theinsulating coating of the coated wire at the area of contact, and permitthe establishment of etective electrical Contact between the conductorand the spring wire of the helix. As illustrated in Figure 1 inconnection with helix 10c, the end portion of the wire 12 may then beanchored around the spring wire extension between helices 19C and 10d;or, alternatively, this portion of the wire may simply be snipped oifand removed.

It will be apparent that each of the helices of the device of Figures 1and 2 is open at both ends, so that insulated conductors may be insertedfrom either side of the connector. The specic angle a between the axisof the individual helix and the longitudinal axis of thc compositeconnector device, as shown in Figure 1, is of no particular significanceso long as the ends of the individual helices are out of line withadjacent helices for effective accessibility. Figure l represents astructure with approximately the minimum angle for easy access to eachhelix where the helices are close together as illustrated. The angle maybe increased to a full degrees if desired. Some variation in angle forindividual helices may also be tolerated; but since'unitorm angles areeasily and most conveniently provided by automatic coil Windingmachinery, the structure illustrated is easily producible and ispreferred.

Any number of helices may be combined together in structures such as areillustrated in Figures l and 2; and hence any desired number ofconductors may be connected with such devices. in telephonecommunication cables it is frequently necessary to connect togetherthree wires. Connectors such as shown in Figures 1 and 2 and having amuch larger number of individual helices are conveniently separated intogroups of lesser numbers of helices by twisting or bending the springwire at points 16, the wire being lightly but effectively scored at suchpoints for the purpose. Thus there is provided a substantiallycontinuous source of springconnector assemblies having any desirednumber of connector units per assembly.

In a typical connector designed for the interconnection of telephonecable conductors, the spring wire was a tin plated steel spring wirehaving a diameter of 0.931. Each helix had an outside diameter of 0.138and consisted of four contiguous turns or coils. The wire extensionconnecting adjacent helices was approximately 17/16 long and was notchedat approximately the center. Such a connector was found to provideeffective connection to insulated copper wire of a size equivalent toNo. 19-No. 26.

It is to be noted that the diameter of the spring-wire represents asubstantial proportion of the diameter of the helix. In the specificexample, the ratio of wirediameter to internal diameter of the helix is.G3i/.076, or 41%. Adequate strength and rigidity is ordinarilj,lprovided with spring-wire having a diameter of approximately one-thirdto one-half the internal diameter of the cylindrical helix. In allcases, the size and strength of the spring wire is so selected as tocause displacement of insulation from insulated conductors which may beinserted within the helix.

For telephone communication work, where very low current ow ispermitted, spring steel wire, particularly when plated with zinc, tin,nickel, silver or other metallic corrosion resistant finish has beenfound to be fully effective. Phosphor bronze, beryllium bronze, siliconbronze, and hard copper are useful where greater current carryingability is required.

Figures 1 and 2 illustrate the connection of but a single insulatedconductor at an individual helix. Two or more conductors may beconnected within a single helix, in

which case a somewhat larger number of coils is usually preferred. Sucha connection requires that the different conductors be individuallypositioned between different contiguous pairs of coils, and hence thatsome of the conductors must be advanced much farther than others alongthe helix.. Such a method of inserting the conductors is undulytime-consuming if the conductors are inserted from the same end, or, ifboth ends of the helix are used, difficulty in holding the connector isusually encountered. A preferred structure employs a compound helixymade of two or more interspaced spring wires, as shown in Figures 7 and8. The connector 70, here illustrated, consists of two separate helicesformed of spring wires 71 and 72 close-wound into a single unit, the twobeing sealed together at one end as indicated at 73. Longer helices maybe similarly bonded centrally rather than terminally. The free end ofeach of these wires 71 and 72 projects from the open end ofthe helix,forming a wedge shaped throat opening into which an insulated conductormay be slidably advanced.

In use, two conductors are threaded axially through the compound helix70. The end segment of one conductor is forced into the throat openingbetween the extended end of the spring-wire 71 and the outer coil ofspring-wire 72, and the end segment of the other is similarly forcedinto the opposite throat opening. Slidably advancing each wire around asingle turn of the helix produces a fully effective connection.

The connector of Figures 7 and 8, like that of Figures l and 2, isdesigned primarily for interconnecting a multiplicity of insulatedconductors. On the other hand, the connector devices of Figures 3-6 aredesigned primarily for use in connecting one or more insulatedconductors to a bolt, binding post, bus bar, or other electrical outlet.The connector 39 of Figure 3 is provided with an eyeshaped member 31 formounting on a suitable bolt or binding post. Connector 40 of Figure 4has a straight prong type terminal 41 for insertion into a suitable jackor eyelet. Connector 50 of Figure 5 is provided with a second helixmember 51 terminating in a handle member 52, for connection to a post orpin S3. The helix 51 grips the post 53 tightly, but may easily beremoved by application of torque to the handle 52, thereby expanding thehelix. Figure 6 illustrates a connector 6ft terminating in an extendedconnector portion 61 indicated as being spirally fastened to ya barconnector or bus bar 62.

In each of the foregoing alternative examples, the spring connectormember comprises a plurality of contiguous equal coils and at least oneterminal extension providing a wedge-shaped throat opening betweeny thespring wire of the extension 'and the corresponding portion of thespring wire of the adjacent end coil. This wedge-shaped opening, aspreviously indicated, provides for the entry of a segment of theinsulated connector between the contiguous tightly compact coils.

There has therefore been provided a new and useful spring connectordevice suitable for forming permanent electrical connections toinsulated conductors without any necessity of rst removing any portionof the insulation. The high spring tension available inthe device notonly provides for effective displacement of most types of insulationfrom the copper wire or other conductor, but 'also produces andmaintains completely adequate electrical connection with such conductor.Long continued vibration, handling, or other types of mechanicalstressdo'not destroy or weaken the electrical connection thus provided,but on the contrary serve to Hatten the conductor and thereby toincrease thetotal area of contact between conductor and connector.Connections are easily `and quickly made by hand, without the use ofapplicators or other tools. A neat and compact connection is produced,which can be adequately and effectively protected and insulated eitherby wrapping with adhesive tape or in other ways.

What is claimed is as follows:

1. A spring-wire connector suitable for forming a permanent electricalconnection between insulated conductors as herein described andconsisting essentially of a series of close-wound cylindricalspring-wire helices whose longitudinal `axes are parallel and spacedapart, the springwire having sufficient strength to cause displacementof insulation from an insulated conductor, and contact between thespring-wire and the conductor, on slidably forcing the insulatedconductor along the contacting springwire surfaces; each helix beingdisplaced from adjacent helices to an extent permitting free access tothe open interior of the helix from either end thereof; adjacent helicesbeing connected together by an extension of the spring-wire from an endcoil in a tangential plane and at an angle with the plane of the coiljust suflicient to enable the insulated conductor to be easily slidbetween the extension and the end coil; the spring-wire extension beinglightly notched between adjacent helices to permit separation bybending.

2. A spring-wire connector suitable for forming a permanent electricalconnection between insulated conductors as herein described andconsisting essentially of a series of close-wound spring-wire helices,the spring-wire having suliicient strength to cause displacement ofinsulation from an insulated conductor `and Contact between thespring-wire and the conductor on slidably forcing the insulatedconductor along the contacting spring-wire surfaces, the helices beingopen-ended and sufliciently separated from each other to permit freeaccess to the open interiors thereof, and the spring-wire forming eachof said helices being extended from an end coil of the helix at anincreased pitch angle and forming a wedge-shaped Y throat openingbetween the extension and the end coil enabling an insulated conductorpassing axially through the helix to be easily slid between theextension and the end coil.

3. A spring-wire connector suitable for forming a permanent electricalconnection between insulated conductors as herein described andconsisting essentiall-y of a close-wound compound *helix of at least twospringwires forming alternate coils of said helix, the springwireshavingv sufficient strength to cause displacement of insulation from aninsulated conductor and contact between the spring-wire and theconductor on slidably forcing the insulated conductor along thecontacting spring-wire surfaces, the spring-wires each being extended ata common end of the helix at an increased lpitch angle and forming awedge-shaped throat opening between the extended wire and thecorresponding segment of the adjacent close-wound end coil, enablinginsulated conductors passing axially through the helix each to be easilyseparately slid between an extended springwire and its adjacent coil.

4. In combination, a spring-wire connector and an insulated wireconductor in electrical connection therewith, said connector comprisinga close-wound contiguous-coil cylindrical helix having an internaldiameter sutiicient to allow easy entry of said i-nsul-ated wire andformed of spring-wire having a diameter of about onethird to aboutone-half of said internal diameter, said spring-wire being extended fromat least one end coil of said helix at an increased pitch angle andforming a wedge-shaped throat opening between the extension and the endcoil of a size suiiicient to enable said insulated wire to be easilyslid between the extension and the end coil, said insulated wireconductor lying partly within said helix and emerging from within saidhelix between twol adjoining turns or coils thereof, the insulation onsaid wire conductor being displaced and the conductor being inelectrical connection with said two turns at the area of emergence ofsaid conductor from said helix.

5. In combination, a spring-wire connector and an insulated wireconductor in electrical connection therewith; said connector comprisinga close-wound contignous-coil cylindrical spring-wire helix, thespring-wire having suiiicient strength to cause displacement ofinsulation from an insulated conductor, and Contact between thespring-wire and the conductor, on slidably forcing the insulatedconductor between adjoining coils, the spring-wire being extended fromat least one end coil of the helix' at an increased pitch angle andforming a wedge-shaped throat opening between the extension and the endcoil, and at least one extension terminating in mounting means formounting said connector to an electrical outlet; and said insulated wireconductor axially entering said helix at an open end thereof andemerging from said helix between two adjoining coils thereof, theinsulation on said conductor being displaced and the conductor being inelectrical connection with said two coils at the area of emergence.

UNITED STATES PATENTS Thompson May 12, 1885 Wooldridge `et al. Jan. 9,1906 Read Apr. 28, 1908 Forrester lan. 11, 1927 Wood Apr. 5, 1949Dubilier Apr. 21, 1951 Blomstrand Oct. 20, 1953 Ripley Apr. 1, 1958FOREIGN PATENTS Great Britain Nov. 17, 1921

